Radio system



March 15 1921. 1,621,062

1.. w. cause RADIO SYSTEM Filed June 17 1920' WITNESSES: -INVENTOR 1.7M LBW/Ii Warr/k yibzz C/zubb ATTORNEY Patented Mar. 15, 1927.

UNITED PATENT ()FFIC'E.

LEWIS EARRING-TQM CHUBB, 3F EDGE'WOOD TFARK, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC & MAETUFACTURING- COMPANY, A COREORATION OF PENNSYLVANIA.

RADIO SYSTEM.

Application filed June 1?, 1920. Serial No. 389,580.

My invention relates to the transmission and reception of radio or wireless signals. whereby a message may be sent and received with practical secrecy and without interference with messages simultaneously sent by other stations lying within the range of radio activity.

More particularly, my invention relates to the transmission and reception ofradio or wireless signals by means of trains of radio waves. wherein radio waves of different frequencies are employed and the wave trains or impulses impressed upon these waves are likewise of differing frequencies all above the range of audibility, and to means for combining these wave trains to produce beats of audible frequency.

My invention also relates to the transmission and reception of radio or wireless signals employing the same wave length but in which the wave tr ins are displaced.

Heretofore. radio waves of differentlengths but of the same train frequency have been emplo ed to effect secrecy of wireless communication. As a variation to this method. wave trains of the same frequency but differing in phase were impressed on these radio waves of unequal length. This difference in phase relation of the wave trains operated to effect an annular displace ment between mirrors enabling: signals to be caught visually by reflected beam of lia'ht. As a method for eliminating: static effects at the receiving station. radio waves of constant frequency have been received and heterodvned by electron tubes to produce beats above the reuse of audibilitv and these ave trains above the of audibility imposed upon a closed circuit. whereby they interacted to produce an audible beat.

An object of my invention is to provide a system for wireless communication, whereby a plurality of different wave lengths be employed to send a message. thus necessitatingr tuning at the receiving station to each of the wave lengths separately. By tuning to a plurality of wave lengths" interference of the message by other messages sin'iultaneously sent from a differentstation is reduced to a minimum Again. by reason of the great selectivity in tuning and because of the practical difliculty in obtaining; the exact combination, owing to the wave train frequency of each radio wave being above audible frequency reception by unauthorized stations is unlikely.

The number of sending devices now in use is so great that any receiving system tuned to a single frequency, while it may reproduce the signals radiated on a single frequency is likely to have such signals confused by interference from other stations. On the other hand, a station, equipped with two receiving circuits" tuned respectively to the two wave lengths used by the sending station and obtaining a. signal by the interaction of these two wave lengths, is far less likely to be disturbed by interference and so will obtain the message.

To this extent, the system is a secret one. since only the receiving station acquainted with the two wave lengths can obtain the message clearly, other stations being able to obtain it only with difiiculty because of their inability to escape interference.

With these and other objects in view, which may be incident to the improvements my invention consists in the parts and combin-ations to be hereinafter set forth and claimed, with. the understanding that the several necessary elements comprising my invention may be varied in their arrangement without departing from the spirit and scope of the appended claims.

In order to make my invention more clearly understood, I have shown in the accompanying drawings, means for carrying it into practical effect without limiting the improvements, in their useful applications to the particular constructions which for the purpose of explanation, have been made the subject of illustration.

Fig. 1 is a diagrammatic view of the sending apparatus; Fig. 2 is a diagrammatic view of one form of the receiving apparatus; Fig. 3 is a. diagrammatic view of a modification of the form of receiving apparatus shown in Fig. 2.

In Figs. 1 and 2 I have indicated an arrangement for the carrying out of my invention in the application thereof to either a wireless telephone or telegraph system.

Referring more particularly to Fig. 1; in

circuit with a sending antenna 1 is a variable inductance 3, afixed lnductance 4 and a variable capacitance 5; correspondingly in" circuit with a sending antenna 2 is a variable inductance 6, a fixed inductance 7 and a variable capacitance 8. By varying the amount of inductance and capacitance in these circuits, they may be tuned to any desired dififering Wave lengths. The fixed inductance lis inductively coupled to a variable inductance 9, one terminal of which is connected to a filament 10 of an electron tube containing a grid 11 and a plate or Wing 12. The filament 10 is heated by a suitable battery 13. Two inductances l4 and 15 term the mutual inductance between the plate and grid circuits necessary for the sustained oscillation desired in the use of electron tubes as generators of radiodrequency current. A variable capacitance 16 is inserted in the plate-current circuit to enable careful tuning to be done. Main lead Wires 17 and 18 from a suitable source of direct current are connected, respectively. to the plate and the filament. Likewise. the fixed inductance T is inductively coupled to a variable indur tance 19, one terminal of which is connected to a filament 20 of an electron tube having a grid element 21 and a plate or Wing 22. The filament 20 is heated by a suitable battery 23. Two inductances 2i and term the mutual inductance betwee the plate and grid circuits necessary tor the sustained oscillation desired in the use of elec tron tubes as generators radio-frequency current. A variable capacity 26 is inserted in the plate-current circuit to enable careful tuning. Main lead Wires 27 and 28 conduct a direct current from a suitable source to the plate and filament.

From the foregoing, it will be apparent that the two electron tubes are connected to the source of direct current to constitute generators of high-frequency alternating current. In the first mentioned tube. the l frequency alternating" current. pass tween the plate 12 and the hot filament passes through the variable inductance and because of its inductive conpli the fixed inductance a of the antenna c of antenna 1. it sets up therein hiygh-- quency radio oscillations. The adiustinent ot' the variable inductance 9 and the variable capacitance 16 will allow an ad 'ustment or the period of oscillation of the plate-current circuit. Likewise, an adjustment of the variable inductance 3 and variable capacitance 5 in the antenna circuit of the -.i...'Cllll2 2 u .ll permit the tuning of this circuit to the nave circuit in. larger number o'i con'nnutator segments than t i'intennaa l and 2 are l6 interrupter Q9. grounded, either through microphone or telegraph key 32. The purpose 0 the dili'erence in the no. 'iher of conunutatior segments in circuit interrupters and Fall is to give a difi'ercnce in the wave-train tircqueucv lit is obvious that the same result could be obtained by rotating the intcrrimters at dl'fi "l erent rate. The rates of the Wave trains given out are above the range of udibil and it is this .i'eatnre ot m invention that renders it peculiarly eliertive for the secret transmission of mrssages. If desired. instead of employing separate antennzc an other type of antenna may be used. Moreover. any radio-frequency generator other than electron tubes may be used, such as the Poulsen arc and liigluirexpieucv alternating-current generators.

Referring HOW to Q. which illustrates an arrangement ot a receiving station f rying my invention. there vided receivi antennae 34 and the autemia comprises r enua circuit or riablc in uctance 3G. a fixed inductance in and a va .ble capacitance The antenna circuit of antenna 37 compris s a variable ind ectance a fixed inductance l0 and a van-- able capacitance ll.

lnduetiveh coupled to the fixed inductance l? is a variable inductance The inductance es iorin part of a circuit including a variable capacitance 43. a fixed capacitance it and a grid hem-cut oi an electron tube having a filament 41- ind a plate 47. The filament 4% is heated hv means of a battery in circuit vvith i fil{1 !1(llt through a vari ale resistance A battery pla :s a positive potent" (l he plate it". Within eoupl fined inductance 40 is a variable i The ind ctance forms part ot a cuit includin variable cauacit v 53. a fixed capacitanc" V1: and a grid 05 of an electron tube havin a filament and a plate The vfilaine i is heated by means of a bah terv 58 in circuit with the filament through a variable resistan e A. positive potential is appli jl to the plate element 57 bv men is or a be err 60. ll ithin the plate circuit is a fixed inductance til.

It ill be apparent to one skilled in the art, from an inspection of the above described connections, that the two electron tubes are here connected to constitute amplifiers of the high-frequency alternating current received by the antennae 3i and fry ductively connected to the inductance 51 a variable inductance 62 in circuit with a v able capacitance 6S and the telephone l'QCnJV- ers 64 between the terminals of which is con nected a variable capacitance 65. The inductance 61 is likewise inductively couples to a variable inductance 66 which is in series with a variable capacitance 67 and the terminals of the telephone receiver 64:. The circuit (33 and 64 is tuned to the frequency of he antenna circuit e1, oo, 37 and 38. In like manner, circuit 66, 67 and ti t is tuned to the frequency of the antenna circuit 353, 3.), 4-0 and 41. As in case of the transmitting apparatus, instead of employing separate antennae, any other form of antenna may be employed, if desired.

From the foregoing, it will be clear that radiowaves of different radiofrequency are set up in the transmitting antenna circuits by means of electron tubes acting as highfrequency generators, the antenna 1 deriving its wave oscillations through the inductance 4, inductively coupled to the variable inductance 9 through which pass oscillations of radiofrequency from one of the electron tubes. Likewise, the antenna 2 derives its wave oscillations through the inductance 7 coupled to the variable inductance 19 through which pass oscillations of a different radiofrequency from the other electron tube. The antenna circuit consisting of the antenna 1, the variable inductance 3, the fixed inductance 4: and the variable capacitance 5 is interrupted by the rotary circuit breaker 29- which revolves at a speed that gives to the wave trains a frequency above the range of audibility. Similarly, the antenna circuit consisting of the antenna 2, the variable inductance 6, the fixed inductance 7, the variable capacitance 8, has its radio waves broken up into wave trains of a frequency above the range of audibility by the circuit breaker 30. The frequency of the wave trains in the two antenna circuits are different. Either by the microphone 31 or the telegraph key 32, signals are impressed upon these two differing wave trains. The receiver is tuned to a plurality of radiofrequencies corresponding to those of the transmitter. The oscillations set up in antenna circuit including the antenna 3%, the variable inductance 36, the fixed induc tance 37. and the variable capacitance are transmitted through the vaciunntube amplifier to the circuit, variable inductance F52, variable capacitance 63 and telephone receiver 64. This last mentioned circuit is in tune with the antenna circuit. Antenna circuit comprising the antenna 35, the variable inductance 39, the fixed inductance 40, the variable capacitance 4:1, is tuned to another of the transmitted radiofrequencies, and the oscillations set up in this circuit are transmitted, through the electron-tube amplifier, to the circuit containing the variable inductance 66, the variable capacitance 62', and the telephone 54, which is in tune with this last mentioned antenna circuit.

When radio waves of differing frequencies, broken up into wave trains of differing frequencies the train frequencies lying above the limit of audibility are sent out from the transmitting station they set up, within the tuned circuits of the receiver mechanism, oscillations. lVithin the tuned circuit comprising the variable inductance 62, the variable capacitance 63, and the telephone 64:, these oscillations are set up. Likewise, within the tuned circuit including the variable inductance 66, the variable capacitance 67, and the telephone 46, oscillations corresponding to the other wave length are set up. These oscillations in the two last mentioned circuits are in the form of trains of oscillations. the train frequency being, in each case, above the ran e of audibility, but, at the common connection which is through tle telephone 64., these wave trains will interfere to form a heat within the range of audibility, and, therefore, signals may be received through the telephone receiver.

Referring to the modification of the receiving mechanism shown in Fig. 3 of the drawings, the connections of the receiving antenna and of the amplifiers are like that shown in 2. However, in this niodification, the circuit tuned to the frequency of waves received in antenna circuit including the antenna 34, the variable inductance 36, the fixed inductance 37, the variable capacitance 38, is the circuit comprising a variable inductance G9, a variable capacitance 70, a fixed capacitance 71, shunted by a resistance '22 and a grid element 73 of an electron tube. Likewise, the circuit tuned to the antenna circuit including the antenna 35, the variable inductance 39, the fixed inductance 40, the variable capacitance 41 is the circuit *on'qnrising a variable inductance 74:, a variable capacitance 75, a fixed capacitance 6, shunted by a resistance 77 and another grid element 78 of the same electron tube. Within the electron tube is a filainent 79 heated by battery 80 through a variable resistance. The plate circuit of this tube consists of a battery 81, the positive terminal of which is connected to a plate or wing 82. Within the circuit in cluding the filament 79 and the plate 82 are mounted telephone receivers 83. Upon re ceiving radio waves of the correct frequency, the circuit including the grid 73 is set in periodic vibration according to the number of wave trains sent out from the sending station. Again, the circuit including the grid elen'iert 78 has periodic oscillations set up therein corresponding to the frequency of the wave trains sent out over the circuit of similar tuning at the transmitting station. These oscillations in the two grid circuits separately, would produce oscillations in the telephone 83 above the range of audibility but, because of their interaction, there are produced beats within the range of audibility and thus signals are received in the telephone.

I wish. it expressly understood that, whereas I have, for the purpose of simplicity, illustrated my invention as applied to the sending and receiving of but two radiowave frequencies and but two train frequencies, a greater number could be employed. 'lhe arrangen'ient of apparatus for a plurality of different wave lengths and train frequencies exceeding two will be apparent to those skilled in the art.

While I have described certain embodiments of my invention, it is apparent that many modifications may be made thereunder by those skilled in the art without departing from the spirit thereof, and I desire, therefore, that my invention be limited only as set forth in the appended claims or by the showing of the prior art.

I claim as my invention 1. In a system for wireless comn'iuuication, the combination of means for propagating a plurality of wave trains of different radiofrequency and different train frequency, with means for receiving the wave trains, means for causing the wave trains to interact to produce a beat of audible frequency, and means for receiving the beat.

2. In a system for wireless communication, the combination of means for propaga ting a plurality of wave trains of different train frequency, the train frequency being above the range of audibility, with means for receiving the wave trains, means for causing the wave trains to interactto produce a beat of audible frequency, and means for receiving the beat.

3. In a system for wireless communication, the combination of means for propagating a plurality of wave trains of different radiofrequeney and diiferent train frequency, the train frequency being above the range of audibility, with receiving antennae tuned to a plurality of frequencies, means for causing the received wave trains to interact to produce a beat of audible frequency, and means for receiving the beat.

a. In a system for wireless communication, the combination of means for propagating a plurality of wave trains of different radiofrequency and different train frequency, the train frequency being above the range of audibility, with receiving antennae tuned to a plurality of frequencies, amplifiers coacting with the antenna circuits, means coacting with the amplifiers to cause the wave trains to interact to produce a beat of audible frequency, and means for receiving the beat.

5. In a system for wireless communication, the combination of means for propa gating a plurality of wave trains of different indiofrequency and different train frequency, the train frequencies being above the range of audibility, with means for receiving said wave trains, two circuits tuned to the frequency of the received radio waves, and means at their point of interaction for combining the train-frequencies to produce a beat of audible frequency.

6. In a system for wireless communication, the combination of means for )ropagating a plurality of wave trains of different radiofrequency and different train frequency, the train frequencies being above the range of audibility, with means for receiving said wave trains, two interacting circuits tuned to the frequency of the received radiowaves, an electron tube, two grids vithin the electron tube in operative relation with the two interacting circuits, and means for receiw ing the beat produced by the interaction of the wave trains.

7. In a system for wireless communication,

the combination of means for propagating a plurality of wave trains of different radiofrequency anu different train frequency, the train frequency being above the range of audibility, with receiving antennae tuned to a plurality of frequencies, two interacting circuits tuned to the frequencies of the re ceived radio waves, and means at their point of interaction for producing from the differing train frequencies a beat of audible frequency.

8. In a system for wireless conmmnication, the combination of means for propagating aplurality of wave trains of different radiofrequency and different train fre quency, the train frequency being above the range of audibility, with antennae tuned to a plurality of frequencies, amplifiers coacting with the antenna circuits, two interacting circuits coacting with the amplifiers and tuned to the frequencies of the received radiowaves, and means at their point of interaction for producing therefrom a beat of audible frequency. equal to the beatfrequencv of the said ti'ain-ii'requencies.

9. In a system for wireless communication, the combination of means for propagating a plurality of wave trains of different radiofrequency and different train frequency, the train frequencies being above the range of audibility, with receiving; antennae tuned to a plurality of frequencies. interacting c1rcuits tuned to the frequencies of the received radiowaves. an electron tube, grids within the electron tube coacting with the interacting tuned circuits, whereby a beat of audible frequency is produced in the plate circuit of the electron tube from the interaction of the differing train frequencies.

10. In a system for Wireless communication, the combination of means for propagating a plurality of Wave trains of different radiofrequency and dili'erent train frequency, the train frequencies being above the range of audibility, with receiving antennae tuned to a plurality of frequencies, amplifiers cooperating with the antenna circuits, interacting circuits tuned to the frequencies of the received radioWa-ves and co-operating With the amplifiers, an electron tube, aplurality ofgrids Within the electron tube coacting With the interacting tuned circuits, whereby a beat of audible frequency is produced in the plate circuit of the electron tube from the interaction of the difiering train frequencies and means for indicating the presence of said beat.

11. In a system for Wireless communication, the combination of a plurality of antennae tuned to plurality of frequencies, with means for propagating Wave trains therein at different rates, one rate for each antennae, means for receiving said Wave trains, and means for causing the Wave trains to interact to produce an audible beat.

In testimony whereof, I have hereunto subscribed my name this 27th day of May 1920.

LEWVIS VVARRINGTON CHUBB. 

